Contact detection mode switching in a touchscreen device

ABSTRACT

A method is disclosed for determining detecting a conductive object and determining the type of object and the type of contact that object has with a touch sensitive surface, the method comprising measuring capacitance on a plurality of mutual capacitance sensors, each mutual capacitance sensor corresponding to a unit cell in an array of unit cells. After mutual capacitance is measured a peak unit cell is identified based on the measured capacitances and a matrix sum of a plurality of unit cells surround the peak unit cell is calculated. The value of the peak unit cell and the matrix sum are then compared to a range and a contact type determined based on the comparison.

RELATED APPLICATION

This patent application claims the benefit of U.S. Provisional PatentApplication No. 61/890,738, filed Oct. 14, 2013, U.S. Provisional PatentApplication No. 61/890,745, filed Oct. 14, 2013, U.S. Provisional PatentApplication No. 61/890,753, filed Oct. 14, 2013, U.S. Provisional PatentApplication No. 61/890,757, filed Oct. 14, 2013, U.S. Provisional PatentApplication No. 61/890,794, filed Oct. 14, 2013, U.S. Provisional PatentApplication No. 62/004,724, filed May 29, 2014, U.S. Provisional PatentApplication No. 62/028,393 filed Jul. 24, 2014, U.S. Provisional PatentApplication 62/039,308, filed Aug. 19, 2014, U.S. Provisional PatentApplication No. 62/039,796, filed Aug. 20, 2014, and U.S. ProvisionalPatent Application 62/042,678, filed Aug. 27, 2014, each of which isincorporated by reference herein in its entirety.

TECHNICAL FIELD

This disclosure relates generally to electronic systems, and, moreparticularly, touchscreen interfaces and operation.

BACKGROUND

Capacitance sensing systems can sense electrical signals generated onelectrodes that reflect changes in capacitance. Such changes incapacitance can indicate a touch event (e.g., the proximity of an objectto particular electrodes). Capacitive sense elements may be used toreplace mechanical buttons, knobs and other similar mechanical userinterface controls. The use of a capacitive sense element allows for theelimination of complicated mechanical switches and buttons, providingreliable operation under harsh conditions. In addition, capacitive senseelements are widely used in modern consumer applications, providing userinterface options in existing products. Capacitive sense elements canrange from a single button to a large number of sensors arranged in theform of a capacitive sense array for a touch-sensing surface.

Transparent touch screens that utilize capacitive sense arrays areubiquitous in today's industrial and consumer markets. They can be foundon cellular phones, GPS devices, set-top boxes, cameras, computerscreens, MP3 players, digital tablets, and the like. The capacitivesense arrays work by measuring the capacitance of a capacitive senseelement, and looking for a change in capacitance indicating a touch orpresence of a conductive object. When a conductive object (e.g., afinger, hand, or other object) comes into contact or proximity with acapacitive sense element or surface above a capacitive sense element,the capacitance changes and the conductive object is detected. Thecapacitance changes of the capacitive touch sense elements can bemeasured by an electrical circuit. The electrical circuit converts thecapacitances of the capacitive sense elements into digital values.

SUMMARY

A method is disclosed for determining detecting a conductive object anddetermining the type of object and the type of contact that object haswith a touch sensitive surface, the method comprising measuringcapacitance on a plurality of mutual capacitance sensors, each mutualcapacitance sensor corresponding to a unit cell in an array of unitcells. After mutual capacitance is measured a peak unit cell isidentified based on the measured capacitances and a matrix sum of aplurality of unit cells surround the peak unit cell is calculated. Thevalue of the peak unit cell and the matrix sum are then compared to arange and a contact type determined based on the comparison.

A user interface device is disclosed that comprises a first pluralitycapacitance sensing electrodes disposed along a first axis of an array,a second plurality of capacitance sensing electrodes disposed along asecond axis of an array, and a controller. The controller may beconfigured to measure capacitance on a plurality of mutual capacitancesensors, each mutual capacitance sensor corresponding to a unit cell inthe array of unit cells. After the controller measures identifies thepeak unit cell based on the measured capacitances, it may calculate amatrix sum of a plurality of unit cells surround the peak unit cell. Thevalue of the peak unit cell and the matrix sum are then compared to arange and a contact type determined based on the comparison.

A touchscreen controller is disclosed that may be configured to measurecapacitance on a plurality of mutual capacitance sensors, each mutualcapacitance sensor corresponding to a unit cell in the array of unitcells. After the controller measures identifies the peak unit cell basedon the measured capacitances, it may calculate a matrix sum of aplurality of unit cells surround the peak unit cell. The value of thepeak unit cell and the matrix sum are then compared to a range and acontact type determined based on the comparison

DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a representation of self capacitance, according toone embodiment.

FIG. 1B illustrates a representation of mutual capacitance between a rowand a column electrode comprised of diamond-shaped sense elements,according to one embodiment.

FIG. 1C illustrates a representation of mutual capacitance between a rowand a column of bar-shaped electrodes, according to one embodiment.

FIG. 2A illustrates an array of diamond-shaped sense elements arrangedin a two-dimensional array, according to one embodiment.

FIG. 2B illustrates an array of bar-shaped electrodes arranged in a twodimensional array, according to one embodiment.

FIG. 3A illustrates as sensing circuit for self capacitance measurement,according to one embodiment.

FIG. 3B illustrates as sensing circuit for mutual capacitancemeasurement, according to one embodiment.

FIG. 4A illustrates connections between a plurality of sensing channelsand a plurality of measurable capacitances, according to one embodiment.

FIG. 4B illustrates connections between a single sensing channel and aplurality of measurable capacitances, according to one embodiment.

FIG. 5 illustrates a flow of information and control signals in acapacitance sensing system, according to one embodiment.

FIG. 6A illustrates measured changes in capacitance numerically on acapacitance sensing array, according to one embodiment.

FIG. 6B illustrates measured changes in capacitance graphically on acapacitance sensing array, according to one embodiment.

FIG. 6C illustrates a plurality of detected peaks on a capacitancesensing array, according to one embodiment.

FIG. 6D illustrates a centroid calculation with a 5×5 window of sensors,according to one embodiment.

FIG. 6E illustrates the result of a centroid calculation with a 5×5window of sensors for two conductive objects, according to oneembodiment.

FIG. 6F illustrates a representation of tracking a plurality ofconductive objects moving across a capacitance sensing array.

FIG. 7A illustrates a stack-up of a touchscreen, according to oneembodiment.

FIG. 7B illustrates a touchscreen system, according to one embodiment.

FIG. 8A illustrates contact timing diagrams for tap, double-tap, andclick-and-drag gestures, according to one embodiment.

FIG. 8B illustrates a plurality of conductive objects moving across acapacitance sensing array to produce a “rotate” gesture, according toone embodiment.

FIG. 8C illustrates a plurality of conductive objects moving across acapacitance sensing array to produce a “pinch” or “zoom-out” gesture,according to one embodiment.

FIG. 8D illustrates a plurality of conductive objects moving across acapacitance sensing array to produce a “grow” or “zoom-in” gesture,according to one embodiment.

FIG. 8E illustrates a plurality of conductive objects moving across acapacitance sensing array to produce a “pan” gesture, according to oneembodiment.

FIG. 8F illustrates a conductive object moving across a capacitancesensing array to produce a “next item” or “next page” gesture, accordingto one embodiment.

FIG. 8G illustrates a conductive object moving across a capacitancesensing array to produce a “scroll” gesture, according to oneembodiment.

FIG. 9 illustrates a method for measuring capacitance on a touchscreenand outputting a result, according to one embodiment.

FIG. 10A illustrates an array of unit cells with mutual capacitancedifference values according to one embodiment.

FIG. 10B illustrates an array of unit cells with mutual capacitancedifference values, wherein each value is updated with a 3×3 sum of allvalues about a center value, according to one embodiment.

FIG. 10C illustrates an array of mutual capacitance difference valueswith a first peak unit cell, according to one embodiment.

FIG. 10D an array of mutual capacitance difference values, wherein eachvalue is updated with a 5×5 sum of all values about a center value andan updated peak unit cell, according to one embodiment.

FIG. 11A illustrates a 3×3 matrix of unit cells, according to oneembodiment.

FIG. 11B illustrates a 5-sensor group of unit cells with additionalsensors at each cardinal direction, according to one embodiment.

FIG. 12 illustrates an embodiment for detecting hover and calculatingposition with summed values, according to one embodiment.

FIG. 13 illustrates an array of unit cells with an edge zone, accordingto one embodiment.

FIG. 14A illustrates an array of unit cells with a path of a hoveringcontact an edge zones at each edge of the array, according to oneembodiment.

FIG. 14B illustrates a close-up of the array from FIG. 14A with actual,detected, and corrected paths for a hovering contact, according to oneembodiment.

FIG. 15 illustrates a method for applying various correction factorsbased on a hover contact's presence in an edge zone, according to oneembodiment.

FIG. 16 illustrates a method for applying a common mode filter andverifying a hover detection, according to one embodiment.

FIG. 17A illustrates a method for applying a common mode filter to hoverdata, according to one embodiment.

FIG. 17B illustrates hover data after applying a common mode filter,according to one embodiment.

FIG. 18A illustrates a method for verifying hover detection with selfcapacitance measurement data, according to one embodiment.

FIG. 18B illustrates self capacitance hover data as applied in themethod of FIG. 18A, according to one embodiment.

FIG. 19A illustrates a table of data used for determining which unitcells to include in hover position calculation, according to oneembodiment.

FIG. 19B illustrates an application of an EdgeCutoff from FIG. 19A,according to one embodiment.

FIG. 20 illustrates a method for determining hover location and distancefor hover detections, according to one embodiment.

FIG. 21 illustrates a method for distinguishing and processing a hoverfrom a large object, according to one embodiment.

FIG. 22A illustrates a method for calculating a position of a hovercontact over an array, according to one embodiment.

FIG. 22B illustrates an example of calculation of a position of a hovercontact over an array, according to one embodiment.

FIG. 23A illustrates calculation of a ratio representative of a grip,according to one embodiment.

FIG. 23B illustrates calculation of a ratio representative of a hoverover the edge of an array, according to one embodiment.

FIG. 23C illustrates calculation of a ratio representative of a hovernear the edge of an array, according to one embodiment.

FIG. 24 illustrates a method for calculating and using a ratio ofmeasurements to identify and process various types of contacts,according to one embodiment.

FIG. 25A illustrates maximum values of various contact types on an arrayof unit cells, according to one embodiment.

FIG. 25B illustrates ratios of peaks to 5×5 sum values of various objectand contact types, according to one embodiment.

FIG. 26 illustrates peak values and 5×5 sum values plotted to show modepartitions, according to one embodiment.

FIG. 27A illustrates a plurality of partitions for a device operating infinger mode, according to one embodiment.

FIG. 27B illustrates a plurality of partitions for a device operating inglove mode, according to one embodiment.

FIG. 27C illustrates a plurality of partitions for a device operating instylus mode, according to one embodiment.

FIG. 28 illustrates a method for determining the correct mode of atouchscreen device, according to one embodiment.

FIG. 29 illustrates a process for determining the correct mode of atouchscreen device, according to another embodiment.

FIG. 30 illustrates a state diagram for moving between various states ofa touchscreen device, according to one embodiment.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the embodiments of the present invention discussedherein. It will be evident, however, to one skilled in the art thatthese and other embodiments may be practiced without these specificdetails. In other instances, well-known circuits, structures, andtechniques are not shown in detail, but rather in a block diagram inorder to avoid unnecessarily obscuring an understanding of thisdescription.

Reference in the description to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the invention. The phrase “in one embodiment” located in variousplaces in this description does not necessarily refer to the sameembodiment.

For simplicity and clarity of illustration, reference numerals may berepeated among the figures to indicate corresponding or analogouselements. Numerous details are set forth to provide an understanding ofthe embodiments described herein. The examples may be practiced withoutthese details. In other instances, well-known methods, procedures,processes, and components are not described in detail to avoid obscuringthe examples described. The description is not to be considered aslimited to the scope of the examples described herein.

Capacitance

A capacitor is formed by two conductive plates that are separated by aspace filled with a dielectric material. The capacitance of a capacitormade of two large plates (in farads), C, is given by:

$\begin{matrix}{{C = {ɛ_{r}ɛ_{0}\frac{A}{d}}},} & (1)\end{matrix}$where A is the area of overlap between the two conductive plates (m²), dis the distance between the two conductive plates (m), ε_(r) is thedielectric constant of the material between the two conductive plates,and ε₀ is the electric constant (ε₀≈8.854×10⁻¹² F·m⁻¹). In addition,fringe capacitances along the edges of two adjacent conductive platesadds to the total capacitance therebetween.

In one embodiment, the conductive plates may be conventional metalplates (such as copper electrodes). In another embodiment, theconductive plates may be formed from a transparent conductive material(such as indium tin oxide, “ITO”), silver or carbon ink, or metal mesh.In still another embodiment, a conductive plate may be a human finger orpalm. Any material that is capable of conducting electricity may serveas a conductive plate of a capacitor.

A capacitor can store a charge transferable to other portions of acircuit. The charge stored by a capacitor (in coulombs), q, is given by:q=CV,  (2)where C is the capacitance of the capacitor given in equation (1) aswell as the fringe capacitance and V is the voltage differential betweenthe two conductive plates.

A capacitance may be measured as a self capacitance, the capacitance ofa single conductive plate (electrode) to its surroundings which serve asthe second conductive plate, or as mutual capacitance, the capacitancebetween two specific conductive plates. Self and mutual capacitances maybe changed by the presence of additional conductive plates, such as afinger, in proximity to the conductive plates under test. For thepurposes of this description, conductive plates are referred to as“electrodes” or “sensors.” This is not intended to be limiting ascircuits may describe the conductive plates of a capacitor in differentterms. Additionally, while a finger is a conductive plate for thepurposes of creating a capacitor, it may not be referred to as an“electrode” or “sensor.” While fingers are used in the followingdescription to be representative of the conductive object that is sensedby the capacitance sensor and measurement circuit, other conductiveobjects may be used.

Sensor Construction

FIG. 1A illustrates a representation of self capacitance in a system 101according to one embodiment. An electrode 110 may be disposed on asubstrate 115. A capacitance 117 may exist between electrode 110 and atleast one other electrode 112 according to Equation (1). In oneembodiment, electrodes 110 and 112 may be formed from copper. In anotherembodiment, electrodes 110 and 112 may be formed from a transparentconductive material such as indium tin oxide (ITO). In still anotherembodiment, electrodes 110 and 112 may be formed from silver or carbonink, metal mesh, or another conductive material. Substrate 115 may beglass in one embodiment. In other embodiments, substrate 115 may be aplastic film (such as polyethylene terephthalate, “PET”, or some otherpolycarbonate), a flexible printed circuit board material, or a rigidprinted circuit board material (such as FR4). Substrate 115 may be aseparate layer or it may be part of a larger, integrated system as shownin FIGS. 7A and 7B below. While capacitance 117 is shown to be betweenelectrode 110 and electrodes 112, which are coupled to a ground voltagepotential, one of ordinary skill in the art would understand that thecapacitances between electrodes 110 and 112 may exist at any voltagepotential and that a ground connection is not required. Additionally,although only capacitive coupling between electrode 110 and electrode112 is shown, electrode 110 may capacitively couple to circuit elementsnot shown in FIG. 1A.

FIG. 1B illustrates a representation of mutual capacitance in a system102 according to one embodiment. A first electrode 120 includingmultiple diamond-shaped elements may be disposed on a substrate (notshown) along a first axis. A second electrode 122 including multiplediamond-shaped elements may be disposed along a second axis. In oneembodiment, there may be a mutual capacitance 127 at the intersection125 of the electrodes 120 and 122.

In various embodiments, electrodes 120 and 122 may be formed fromcopper, a transparent conductive material such as ITO, silver or carbonink, metal mesh, or other conductive materials or combinations ofconductive materials. The substrate (e.g., see substrate 115 of FIG.1A), in various embodiments, may be glass, plastic film (such aspolyethylene terephthalate, “PET”, or some other polycarbonate), aflexible printed circuit board material, or a rigid printed circuitboard material (such as FR4). Additionally, among embodiments, thesubstrate may be a separate layer or it may be part of a larger,integrated system as shown in FIGS. 7A and 7B below, for example. In oneembodiment, electrodes 120 and 122 may be disposed on two differentsubstrates that are adhered together. In other embodiments, electrodes120 and 122 may be disposed on two sides of the same substrate or may bedisposed on the same side of a substrate and the connections for eitherelectrode 120 or electrode 122 formed by a jumper between individualelements of electrodes 120 and 122 and disposed over a dielectricmaterial.

FIG. 1C illustrates another representation of mutual capacitance in asystem 103 according to another embodiment. A first electrode 130 may bedisposed on a substrate (e.g., see substrate 115 of FIG. 1A) along afirst axis. A second electrode 132 may be disposed along a second axis.Electrodes 130 and 132 may be bar-shaped in one embodiment. In anotherembodiment, electrodes 130 and 132 may have more complex structures thatare based on the bar-shaped theme. At the intersection of electrodes 130and 132 there may exist a mutual capacitance 137. In one embodiment,electrodes 130 and 132 may be formed from copper. In another embodiment,electrodes 130 and 132 may be formed from a transparent conductivematerial such as ITO. In still another embodiment, electrodes 110 and112 may be formed from silver or carbon ink, metal mesh, or anotherconductive material.

Mutual capacitances 127 and 137 may be used to detect the location ofone or more conductive objects on or near a surface (e.g. FIGS. 6Athrough 6E). An array of mutual capacitances (see description of FIGS.2A and 2B below) may be used to detect one or more conductive objects onan edge of a device with a touch surface. In one embodiment, the edge onwhich the conductive object is placed may be a surface perpendicular tothe substrate on which the electrodes are disposed, as shown in FIG. 7A.

In various embodiments, electrodes 130 and 132 may be formed fromcopper, a transparent conductive material such as indium tin oxide(ITO), silver or carbon ink, metal mesh, or other conductive materialsor combinations of conductive materials. The substrate (e.g., seesubstrate 115 of FIG. 1A), in various embodiments, may be glass, plasticfilm (such as PET or some other polycarbonate), a flexible printedcircuit board material, or a rigid printed circuit board material (suchas FR4). Additionally, among embodiments, the substrate may be aseparate layer or it may be part of a larger, integrated system as shownin FIGS. 7A and 7B below, for example. In one embodiment, electrodes 130and 132 may be disposed on two different substrates that are adheredtogether. In other embodiments, electrodes 130 and 132 may be disposedon two sides of the same substrate or may be disposed on the same sideof a substrate and the connections for either electrode 130 or electrode132 formed by a jumper between individual elements of electrodes 130 and132 and disposed over a dielectric material.

FIG. 2A illustrates an array of electrodes 202 similar to those shown inFIG. 1B. A first plurality of electrodes 220 including multiplediamond-shaped elements may disposed on a substrate (not shown) along afirst axis. A second plurality of electrodes 222 including multiplediamond-shaped elements may disposed on a substrate along a second axis.Close-up 225 illustrates the intersection between the first plurality ofelectrodes 220 and the second plurality of electrodes 222. There may bea mutual capacitance at the intersection an electrode from the firstplurality of electrodes 220 and an electrode of the second plurality ofelectrodes 222 (e.g., like mutual capacitance 127 of FIG. 1B). Thisregion of mutual capacitance may be described as a unit cell 229 of thearray of electrodes 202. Unit cells exist at every intersection and maybe used to detect the location of a conductive object or to detect thepresence of at least one conductive object along an edge of atouchscreen-enabled device as shown in FIG. 7A.

FIG. 2B illustrates an array of electrodes 203 similar to those shown inFIG. 1C. A first plurality of electrodes 230 may be disposed on asubstrate (not shown) along a first axis. A second plurality ofelectrodes 232 may be disposed on a substrate along a second axis.Electrodes 230 and 232 may be bar-shaped in one embodiment. In anotherembodiment, electrodes 230 and 232 may have more complex structures thatare based on the bar-shaped theme. Close-up 235 illustrates theintersection between the first plurality of electrodes 230 and thesecond plurality of electrodes 232. Similar to FIG. 2A there may be amutual capacitance at the intersection an electrode from the firstplurality of electrodes 230 and an electrode of the second plurality ofelectrodes 232 and this region of mutual capacitance may be described asa unit cell 239 of the array of electrodes 203. Unit cells exist atevery intersection and may be used to detect the location of aconductive object or to detect the presence of at least one conductiveobject along an edge of a touchscreen-enabled device as shown in FIG.7A.

Unit cells 229 and 239 and their measured capacitance values may be usedto detect the location of one or more conductive objects on or near asurface (e.g. FIGS. 6A through 6E). An array of unit cells may be usedto detect one or more conductive objects of various types, includingbare fingers, gloved fingers, styli (either active or passive) or anobject hover above the surface. Unit cells may be used individually, incombination, or both to determine object and interaction type.

Unit cells 229 and 239 may be conceptualized geometrically as thesmallest unit of tessellation. That is, the smallest repeatable unit ofmeasurement on the array. Unit cells 229 and 239 may also beconceptualized by stating that every point within the unit cell iscloser to the center of that unit cell (the center of the intersectionbetween the electrodes on different axes) than it is to the center ofany other unit cell. Unit cells 229 and 239 may be conceptualizedfunctionally as the native resolution of the arrays 202 and 203. Thatis, each row and column may be identified and a position defined on eachrow and column. For a rectangular array with twelve columns and ninerows, there may be 108 discrete locations. Since unit cell 229 existsbetween the seventh row (from the top) and the sixth column (from theleft) and unit cell 239 exists at the intersection between the sixth rowand the sixth column, their positions may be given by 6,7 and 6,6,respectively, based on the native resolution of arrays 202 and 203. Unitcells 229 and 239 may be conceptualized as pixels of an array, whereineach pixel may be assigned a location and a measurable value specific tothat location. An example of a pixel-based interpretation of unit cellsis given in FIGS. 6A and 6B below. Unit cells 229 and 239 may also bereferred to as “nodes” wherein each intersection of the row and columnelectrodes is a node of the array. Unit cells may be referred merely asintersections in a mutual capacitance sensing array, as shown in FIGS.2B and 2C. The term “intersection” is merely shorthand for theirconstruction as an intersection between row and column electrodes.

Capacitance Sensing

FIG. 3A illustrates one embodiment of a self capacitance measurementcircuit 301. Self capacitance sensor 310 (C_(S)) may be formed betweenan electrode 110 as shown in FIG. 1A and ground. The non-grounded sideof self capacitance sensor 310 may be coupled to a pin 312 ofcapacitance measurement circuit 301. A switch network 315 may be used togenerate a current by alternately charging self capacitance sensor 310to a voltage (V_(DD)) and discharging the accumulated charge onto anintegration capacitor 322, which may be part of channel 320. The currentfrom switch network 315 and self capacitance sensor 310 may be given by:

$\begin{matrix}{{I = \frac{V}{R_{eq}}},} & (3)\end{matrix}$where the equivalent resistance of the switch network 315 and selfcapacitance sensor 310 is given by:

$\begin{matrix}{R_{eq} = \frac{1}{{fC}_{S}}} & (4)\end{matrix}$where C_(S) is given by equation (1) and f is the switching frequency ofswitches SW1 and SW2. Switch network 315 and integration capacitor 322may be coupled to an input of operational amplifier 324 with a referencevoltage (V_(REF)) to allow step-wise linear charging of integrationcapacitor 322. The voltage across integration capacitor 322 may bemeasured by analog-to-digital converter (ADC) 326, the output of whichmay be analyzed by processing block 330. After the voltage acrossintegration capacitor 322 by ADC 326, the voltage across integrationcapacitor 322 may be reset by switch SW3, allowing a new measurement.

FIG. 3B illustrates one embodiment of a mutual capacitance measurementcircuit 302. Mutual capacitance sensor 311 (C_(M)) may be formed at theintersection of two electrodes (120 and 122 of FIG. 1B; 130 and 132 ofFIG. 1C), which also have a parasitic capacitance 318 (C_(P)). Eachplate of mutual capacitance sensor 311 may be coupled to a pin of mutualcapacitance sensing circuit 302. A first pin 313 may be coupled to asignal generator (TX) 316 and a second pin 314 may be coupled to channel320. The alternating voltage of signal generator 316 may produce acurrent from mutual capacitance sensor 311 to an integrating capacitor322 of channel 320. In one embodiment, the voltage across integrationcapacitor 322 may be measured by ADC 326, the output of which may beanalyzed by processing block 330. After the voltage across integrationcapacitor 322 by ADC 326, the voltage across integration capacitor 322may be reset by switch SW4, allowing a new measurement. In anotherembodiment, the current from mutual capacitance sensor 311 may be usedto bias an input of a self capacitance measurement circuit 301 similarto that shown in FIG. 3A. The bias provided by the mutual capacitanceinduced current may provide greater dynamic range of the combination ofthe integration capacitor 322 and ADC 326.

While channel 320 of FIGS. 3A and 3B are shown to comprise anoperational amplifier (324) and an ADC (326), one of ordinary skill inthe art would understand that there are many ways to measure a voltageon an integration circuit and that the embodiments of FIGS. 3A and 3Bare intended as exemplary and not limiting. For example, ADC 326 may bereplaced by a comparator and a counting mechanism gated by the output ofthe comparator to produce a digital representation of the capacitance onthe integrating circuit. In this embodiment, the number of counts fromthe counting mechanism may represent the time required to charge theintegrating circuit to a reference voltage of the comparator. Largercharging currents may produce faster charging of the integrating circuitand lower count values.

Capacitance measurement circuits such as those in shown in FIGS. 3A and3B may implemented on an integrated circuit (IC) alone or with severalinstances of each to measure the capacitances of a plurality of inputs.

FIG. 4A illustrates a circuit 401 for measuring multiple capacitances411.1 through 411.N according to one embodiment. In circuit 401, fourcapacitances 411.1 through 411.N may be coupled to pins 414.1 through414.N of sensing IC 405. Each mutual capacitance 411.1 through 411.N maybe coupled to channels 320.1 through 320.N and the outputs of each ofchannels 320.1 through 320.N coupled to a processing block 330 throughmultiplexor 410.

FIG. 4B illustrates a circuit 402 for measuring multiple capacitances411.1 through 411.N according to another embodiment. In circuit 402,four capacitances 411.1 through 411.N may be coupled to pins 414.1through 414.N of sensing IC 405. Each capacitance 411.1 through 411.Nmay be coupled to an input of multiplexor 410, the output of which maybe coupled to channel 320. The output of channel 320 may be coupled toprocessing block 330.

FIGS. 4A and 4B illustrate the logical extremes of individual channelsfor each capacitance or a single channel for all capacitances. However,in another embodiment, different combinations of the circuits of FIGS.4A and 4B may be implemented. For example, multiple channels 320 may becoupled to multiple capacitances 411. In one embodiment, thecapacitances may be distributed evenly across all the availablechannels. In another embodiment, the capacitances may be distributedunevenly, with certain channels configured to measure capacitance onmore pins than other channels. Additionally, while FIGS. 4A and 4Billustrate four capacitances, pins, or channels, one of ordinary skillin the art would understand that more or less than four of each may beused. Additionally, the number of capacitances, pins, and channels maybe the same or they may be different, depending on the designrequirements.

Capacitances 411.1 through 411.N may be coupled to signals opposite topins 414.1 through 414.N to produce a current input to channel 320representative of a measured capacitance as described in FIG. 3. Inanother embodiment, capacitances 411.1 through 411.N may be coupled tosignals to produce a current used for calibration of circuits 401 and402.

While FIGS. 4A and 4B illustrate a multiplexor, one of ordinary skill inthe art would recognize that a plurality of switches may be configuredto perform similar functionality as a multiplexor. The representation ofthe mechanism by which capacitances 411.1 through 411.N are coupled tochannel 320 or how channels 320.1 through 320.N are coupled toprocessing block 330 by a multiplexor is merely exemplary and notintended to limit the description to a specific circuit element.

Processing

FIG. 5 illustrates one embodiment of a touchscreen system 501. Atouchscreen 510 may be coupled to a sensing IC 505 though pins 414(e.g., 312 in FIG. 3A, 313 and 314 in FIG. 3B, and 414 in FIGS. 4A and4B). Sensing IC 505 may comprise a channel 320 coupled to thetouchscreen electrodes of touchscreen 510 (illustrated in FIGS. 2A and2B). In one embodiment, the output of channel 320 may be sent to CPU 512for processing (as shown in FIGS. 3A and 3B) and then eithercommunicated to a host 530 through communication interface 516 or storedin a memory 514 and communicated to host 530 through communicationinterface 516 from memory 514. In another embodiment, the output ofchannel 320 may be stored in memory 514 directly (before processing byCPU 512) and either processed by CPU 512 from memory 514 and thencommunicated to host 530 through communication interface 516 orcommunicated to host 530 from memory 514 through communication interface516 without CPU intervention. Tuning and calibration routines may bestored in memory 514 and implemented by CPU 512 through tuning block513. Calibration of signals from touchscreen 510 through and by channel320 may provide capacitance measurement data with greatersignal-to-noise ratios and fidelity to user interactions.

Capacitance measurement data from channel 320 may be representative ofthe total capacitance measured by channel 320. That is, the capacitanceof self or mutual capacitances of FIGS. 1A through 1C may be convertedto a digital value. The digital value may include the parasiticcapacitance (318 of FIGS. 3A and 3B) as well as the native mutualcapacitance with no figure present (311 of FIG. 3B) and the capacitanceof the conductive object or finger. The parasitic capacitance and nativemutual capacitance may be subtracted from the measured value as abaseline to yield difference values that are representative of thecapacitance from the conductive object or finger. Difference values maybe analyzed by processing block 330 to determine if a conductive objectis proximate to the array as well as higher-level user interactions.

CPU 512 or host 530 may further use capacitance and/or difference valuesto detect various types of objects and interactions. In variousembodiments, different levels of data may be communicated to host 530for processing away from CPU 512. While CPU 512 may perform all of theprocessing in the specification below, more or less of the data analysisand manipulation may be off-loaded to host 530 based on the processingrequirements and overhead of CPU 512, host 530, and the system operationgenerally.

FIG. 6A illustrates numerical difference values 601 for a plurality ofintersections 611 of a mutual capacitance sensing array. Numericaldifference values 601 may be derived from the raw values of, forexample, channel 320 (FIG. 3B) for every unit cell (229 of FIG. 2A and239 of FIG. 2B) or mutual capacitance, C_(M), 311 (FIG. 3B). In oneembodiment, numerical difference values may be the difference betweenthe raw count values output from channel 320 and a baseline value. Inone embodiment, the baseline value may be stored globally for the entirearray. In another embodiment, the baseline value may be stored for eachintersection individually. In another embodiment, the baseline value maybe stored for multiple groups of sensors depending on each sensor'sposition on the touchscreen, noise performance of individual sensors,other design restraints. Baseline values may be determined duringdevelopment in one embodiment. In another embodiment, baseline valuesmay be calculated at start-up or may be updated during operation of thetouchscreen to account for variations in noise experienced by thetouchscreen electrodes, physical changes on the touchscreen (heat,humidity, etc.), or other sources of drift in the output channel (e.g.,channel 320).

The numerical difference values 601 of FIG. 6A may be illustratedgraphically as heat map 602 in FIG. 6B. The shade of each cell or mutualcapacitance 601 of heat map 602 may indicate of the numerical differencevalues 601 of FIG. 6A. Darker cells may indicate of greater capacitivecoupling of a mutual capacitance electrode with a conductive object andless capacitive coupling between the mutual capacitance electrodesthemselves. For clarity of description, the representation illustratedin FIG. 6B is used for subsequent figures.

FIG. 6C illustrates an example of peak detection scheme 603 based on thedata from FIGS. 6A and 6B. The peak detection scheme 603 may compareeach unit cell (229 of FIG. 2A and 239 of FIG. 2B) or mutual capacitance611 (FIGS. 6A and 6B) to those around it. Peak detection may use a sumof the surrounding values to provide a common mode filter to peakdetection, as shown FIGS. 10B and 10D. Unit cells or mutual capacitanceintersections with the highest different value may be identified aspeaks and given an identifier and position. A first peak 631 may begiven a first position (X-axis 632 and Y-axis 634). A second peak 635may be given a second position (X-axis 636 and Y-axis 638).

FIG. 6D illustrates an example of centroid calculation 604 wherein anarray of sensors surrounding each peak is defined and processed. Acentroid for each peak may be given by:

$\begin{matrix}{{P = \frac{\begin{matrix}{{S_{i - 2}\left( {i - 2} \right)} + {S_{i - 1}\left( {i - 1} \right)} +} \\{{S_{i}(i)} + {S_{i + 1}\left( {i + 1} \right)} + {S_{i + 2}\left( {i + 2} \right)}}\end{matrix}}{S_{i - 2} + S_{i - 1} + S_{i} + S_{i + 1} + S_{i + 2}}},} & (3)\end{matrix}$where P is the calculated position, i is the unit cell under test, andS_(i) is the signal at each unit cell (under test and surrounding unitcells).

First peak 631 may be used to define a first array 641 including the 25unit cells around and including the unit cell at first peak 631. Secondpeak 635 may be used to define a second array 645 including the 25 unitcells around and including peak 631. The values of first array 641 andsecond array 645 may be processed to find the centroid or center of massof the conductive object based on the values contained within each array(641 and 645). While symmetrical 5×5 arrays are illustrated in anddescribe with regard to FIG. 6D, in various embodiments, the arrays mayhave different dimensions and consequently different numbers of unitcells. Such various embodiments may include 3×3, 4×4, or larger arrays.The arrays may position peaks in the center or the peaks may be offset.Additionally, the arrays may be asymmetrical, with a greater number ofrows or columns, or irregular, where each row or column may have adifferent number of unit cells.

FIG. 6E illustrates an example of the first and second centroids 651 and655 calculated from first and second arrays 641 and 645 of FIG. 6D, whenno virtual sensors are determined activated.

FIG. 6F illustrates an example of two conductive objects 661 and 665moving across a touchscreen and their positions along tracks 663 and667, respectively.

FIG. 7A illustrates one embodiment of a touchscreen stackup oftouchscreen system 501 (from FIG. 5). Touchscreen stackup 701 mayinclude a display 740. Above display 740 may be disposed a sensor layer750. Between sensor layer 750 and a conductive object, such as a fingeror stylus, may be disposed a cover layer 760.

While sensor layer 750 is shown to be on the same layer of a substrate,this is merely exemplary. In one embodiment, sensor layer 750 may bedisposed on the bottom of cover layer 760, reducing the number of layersfrom three to two in touchscreen stackup 701. In another embodiment,sensor layer 750 may be disposed on the top of display 740, alsoremoving a layer from touchscreen stackup 701. In another embodiment oneor both axes of the electrodes shown on sensor layer 750 may be disposedat various depths within the display. For example, sensor layer 750 mayimplemented as in-cell, on-cell, or a hybrid of in-cell and on-cell.Additionally, sensor layer 750 may share certain electrodes with display740.

Touchscreen stackup 701 is illustrated in a touchscreen system 702 inFIG. 7B, according to one embodiment. Touchscreen/display 705 (analogousto touchscreen stackup 701 of FIG. 7A) may be coupled to touchcontroller 710 and display controller/driver 715. Touch controller 710may be configured to sense either self capacitance (FIG. 3A) or mutualcapacitance (FIG. 3B) or both. The output of the touch controller 710may be communicated to an application processor 730. Touch controller710 may also be configured to receive commands and data from applicationprocessor 730. Information that may be communicated to applicationprocessor 730 by touch controller 710 may include the following data foreach identified conductive object on the array:

-   -   Age of Detection—How long (in number of scans) a touch has been        present on the touchscreen;    -   X-Axis Position—The position along the horizontal axis of the        conductive object on the array;    -   Y-Axis Position—The position along the vertical axis of the        conductive object on the array;    -   Z-Axis Intensity—The strength of the touch which may be        indicative of the size of the conductive object or the pressure        with which the conductive object presses against the touch        surface (in some embodiments, Z-axis intensity may be used to        indicate a distance of an object from the surface or sensing        electrodes);    -   Contact Area Major Axis Length—The long axis of an ellipse        centered on the location of the conductive object on the array;    -   Contact Area Minor Axis Length—The short axis of an ellipse        centered on the location of the conductive object on the array;    -   Contact Area Major Axis Angle—The angle (from vertical) of the        long axis of an ellipse centered on the location of the        conductive object on the array;    -   Touchdown/Liftoff Debounce—Whether there is debounce (or        hysteresis) for the detection of the conductive object on the        array and whether/where the detection is within the debounce;    -   Conductive Object Identification—The type of touch (bare finger,        gloved finger, stylus, hover, proximity, etc.);    -   Conductive Object Size—Large conductive object or a        regular-sized conductive object;    -   Virtual Sensor Activation State—identify, location, and signal        level of various active virtual sensors; and    -   Gestures (discussed in more detail with regard to FIGS. 8A        through 8G).        Application processor 730 may also be coupled to display        controller/driver 715 to control what is shown on        touchscreen/display 705.

FIG. 8A illustrates examples of capacitance measurement data for asingle conductive object as might be interpreted to be single-touchgestures. A detection of a conductive object in FIG. 8A is illustratedas a digital ON/OFF or HIGH/LOW of the conductive object on thecapacitance sensor. A single-tap gesture 810 may be detected as apresence of a conductive object detected and then the absence of aconductive object detected to define first touch 811. A double-tapgesture 812 may be detected as a presence of a conductive objectdetected and then the absence of a conductive object detected to definea first touch 811, then within a specified time a second touch 813detected. A click-and-drag gesture 814 may be detected as a presence ofa conductive object detected and then the absence of a conductive objectdetected to define a first touch 811, then within a specific time asecond touch 815 detected. A click-and-drag gesture may also move acursor on a display as the second touch remains on the touch surface andmoves across the surface.

FIGS. 8B through 8E illustrate examples of gestures based on detectionof two conductive objects. In one embodiment, conductive objects 821 and823 may move in a circular motion about some center point, eitherclockwise or counter-clockwise to produce a rotate gesture 802. Inanother embodiment, conductive objects 821 and 823 may move closertogether along a substantially linear path to produce a “pinch” or “zoomout” gesture 803. In another embodiment, conductive objects 821 and 823may move farther apart along a substantially linear path to produce a“grow” or “zoom in” gesture 804. In another embodiment, conductiveobjects 821 and 823 may move along substantially parallel paths toproduce a “pan” gesture 805.

FIGS. 8F and 8G illustrate gestures based on detection of a singlecontact moving across a capacitance sensing array. In one embodiment,conductive object 821 may move in a substantially straight line toproduce a “next item” gesture 806. In another embodiment, conductiveobject 821 may move in a circular motion about some center point, eitherclockwise or counter-clockwise to produce a scroll gesture 807.

Gestures of FIGS. 8A and 8C-8F may be detected on virtual sensors toachieve additional functionality without a user contacting thetouchscreen directly.

FIG. 9 illustrates one embodiment of a method 901 of sensing atouchscreen array and determining the appropriate display. Capacitanceis first measured in step 910. Step 910 may correspond to selfcapacitance measurement or mutual capacitance measurement and may usesensing circuits similar to those described in FIG. 3A or 3B. In otherembodiments, other self or mutual capacitance sensing methods may beused. Raw capacitance values may be used to create a baseline in step920. Baseline values may then be subtracted from the raw capacitancevalues in step 930 to generate difference values (as shown in FIG. 6A).In one embodiment, difference values may be used to determinecalibration parameters for hardware configuration. Calibrationparameters may include coupling various unit cells (e.g. 229 and 239 ofFIGS. 2A and 2B, respectively) to drive signals such that bias currentsare provided to the digital conversion of a measurable capacitance (e.g.FIG. 10, below). Difference values from step 930 may be used todetermine the type of object (e.g. bare finger, gloved finger, orstylus) that has influenced the measured capacitance values as well asthe type of interaction (e.g. contact of hover) in step 940. Once thetype of object and interaction has been determined, the position of thatobject may be calculated in step 950. Successive processing of positionsfrom multiple scans may be used to detect motion of at least one objectover the array of capacitance sensing electrodes in step 960 and themotions of those objects, as well as their mere presence or absence maybe used to determine gestures in step 960 as illustrated in FIGS. 8Athrough 8G. At any of the steps of method 900, data may be communicateddirectly to host 530 of FIG. 5. This may allow for faster processing oroff-load the touch controller (using CPU 512) to perform otherprocessing of analysis of the capacitance sensing information.

In one embodiment, the entire method 901 of FIG. 9 may be completed bytouch controller 710 of FIG. 7. In another embodiment, various steps ofmethod 901 may be completed by an external processor such as applicationprocessor 730 of FIG. 7. In this embodiment, data may be communicated toand from touch controller 710 through communication interface 516 ofFIG. 5. Information communicated to the host may be stored in a memory(such as memory 514) or communicated through a processing unit (such asCPU 512). In another embodiment, additional processing steps may becompleted by touch controller 710 or application processor 730 and theresults of those steps used in performing the steps of method 901illustrated in FIG. 9.

Hover Detection and Processing

A contact hovering over an array of sensors like those shown in FIGS. 2Aand 2B may generate significantly lower difference values than thedifference values shown in FIG. 6A and with far greater relativevariability across the panel and over time. An example of this isillustrated in FIG. 10A, wherein an 8×12 array 1001 of mutualcapacitance sensors (unit cells) 1011 may have difference values with amaximum of 80, unit cell 1021, and a minimum of −9, meaning that thenoise in the system may be such that the measured capacitance isactually lower than the baseline. Because a contact hovering above array1001 may move in a direction perpendicular to a plane defined by thearray and very small movements may have a large impact on the calculateddifference values, an identified peak unit cell (illustrated in FIG. 6C)may move quickly between successive scans of the array, wherein eachscan measures the capacitance of a necessary number of unit cells, orintersections between rows and columns of electrodes.

FIG. 10B illustrates an embodiment of the 8×12 array 1001 of mutualcapacitance unit cells 1011 wherein a value of each intersection isreplaced with a sum difference values about each unit cell. In thisembodiment, the unit cell 1021 now has a value of 275, which is the sumof the previous peak of 80 and the eight other unit cells surroundingthe previous peak and contained within a 3×3 matrix of unit cells 1023.Each unit cell (e.g., unit cell 1011) in the [array 1001 of mutualcapacitance unit cells] may also be summed with its surrounding othereight unit cells, which results in the values shown in FIG. 10B for theunit cell 1021 and the grouping of unit cells 1023. This summing processfor each unit cell may reduce the impact of noise on specific unit cellsby compensating with similarly positioned unit cells in the aggregate.That is, no one unit cell may be too influential on the value used todetermine a peak unit cell that noise experienced by the system orspecific unit cell or electrode may dominate the detection of a peak anda subsequent calculation of a position of a hovering conductive objectabove the array.

FIG. 10C illustrates another embodiment of an 8×12 array 1003 withmutual capacitance values for each unit cell. The unit cell with thehighest value (peak) is 24, corresponding to unit cell 1031 (E4). Inthis example, the peak at unit cell 1031 is only a single unit higherthan three other cells (E5, D6, and E6) and the peak may move with onlya minor movement of a contact over the array 1001 or in response tonoise, causing jitter in the detection and position calculation fromsteps 940 and 950 of FIG. 9.

FIG. 10D illustrates an embodiment of the 8×12 array 1001 of FIG. 10Cwith each of the middle 4×8 unit cells (columns C-F and rows 3-10)summed with the remaining 24 unit cells comprising a 5×5 matrix of unitcells (1033 from FIG. 10C). In this embodiment, the highest value (peak1042) is 362, corresponding to cell E6. Cell E6 has a value 14 unitsgreater than the next highest cell (E5). This means that small changesin the capacitance may be less likely to move the peak, allowing for amore stable window of values for calculating hover position.

FIG. 11A illustrates one embodiment of a 3×3 matrix of unit cells 1101that may be used to calculate a processed capacitance for each unitcell. In the embodiment of FIG. 11A, a unit cell under test, 1111, maybe updated to include the sum of the values of each unit cell within oneunit cell above, below, left, and right of the unit cell under test.Just as illustrated in FIG. 10B for the unit cell from FIG. 10A with avalue of 80, the new value may be 275. While a 3×3 matrix of unit cells1101 is shown in FIG. 11A, one of ordinary skill in the art wouldunderstand that matrices of different dimensions and shapes may be used.Furthermore, while a square fully populated matrix is shown, one ofordinary skill in the art would understand that matrices with roundedcorners (missing cells) may be used. In one embodiment, a 5×5 matrix maybe used (e.g. 1033 of FIG. 10C), including the unit cell under test 1111and the 24 surrounding unit cells. In the example from FIG. 10B, using a5×5 matrix the unit cell with a value of 80 from FIG. 10A would thenhave a value of 445.

FIG. 11B illustrates an embodiment of a 5-unit cell group of unit cells1102 that may be used to calculate a processed capacitance for each unitcell. In the embodiment of FIG. 11B, a unit cell under test, 1112, maybe updated to include the sum of the values of each unit cell immediateabove, below, left, and right of the unit cell under test 1112. In the5-sensor matrix of unit cells 1102, unit cells located diagonal from theunit cell under test may not be included in the processed capacitance.In this embodiment, the example from FIGS. 10A and 10B with a differencevalue of 80 may be updated to be 105.

In another embodiment, a 9-sensor matrix may be used, including valuesof the two unit cells immediately above, below, left, and right of theunit cell under test 1112, In this embodiment, the above example may beupdated to have a processed capacitance of the unit cell under test 1112of 155. In still another embodiment, only the values along diagonalsfrom the unit cell under test 1112 may be used. One of ordinary skill inthe art would understand that various combinations of unit cells may beused that include unit cells representative of the array and the unitcell under test.

FIG. 12 illustrates one embodiment of a method 1200 for generatingprocessed capacitances for unit cells for hover position calculation.Capacitance may be first measured in step 1210. In various embodiments,capacitance may be measured according to FIG. 3A or 3B or other self ormutual capacitance methods useful for determining a change incapacitance as a plurality of intersections of mutual capacitanceelectrodes or at location of self capacitance electrodes. Aftercapacitance is measured in step 1210, each measured capacitance may bestored in a location corresponding to each intersection, or unit cell,in the array in step 1220. The measured capacitance may be stored as theraw capacitance value converted to a digital value in one embodiment. Inanother embodiment, the measured capacitance may be stored as thedifference between the raw capacitance value and a baseline value. Invarious embodiments, the baseline value may be static, dynamic, globalto the entire array of unit cells, specific to each unit cell, or somecombination of each. In step 1230, the value at each unit cell may beupdated as described with regard to FIGS. 11A and 11B, The array maythen be updated with the processed capacitance values in step 1240. Theprocessed capacitance values from steps 1230 and 1240 may then be usedto determine a peak at least at one peak unit cell in step 1250. Thepeak unit cells(s) from step 1250 may then be used to calculate positionof a contact hovering above the capacitance sensing electrodes in step1260. Peak unit cell detection may be completed as shown in FIGS. 10 and11. At various stages, a hover may be detected (as opposed to a touch ofthe surface or some other interaction between a conductive object andthe capacitance sensing electrodes) in block 1201. If a hover is notdetected, before various steps of method 1200, the remaining steps maynot be completed and the capacitance of each electrode or unit cell ofelectrodes may be measured again, or some other processing of thecapacitance values completed.

As a hovering conductive object nears the edge of an array, the amountof capacitance change from the conductive object detected by theelectrodes of the array may drop such that the calculated position of ahovering contact is no longer representative of the actual position.FIG. 13 illustrates one embodiment of an array 1300 of mutualcapacitance sensors 1311 over which an object 1320 is hovering. Themeasured capacitance values of each unit cell may be low enough and withhigh enough variability so as to make position calculation at the edgean array imprecise. Consequently, an edge zone 1330 may be identified inwhich a correction factor may be applied. While a single edge zone 1330is shown in FIG. 13, edge zones may be defined for each edge/axis.

FIG. 14A illustrates an embodiment of an array 1400 of mutualcapacitance unit cells 1411, wherein each axis has two edge zonesdefined at each side of the array. Edge zones 1431 and 1432 may bedefined for positions along the top and bottom of the array. Edge zones1433 and 1434 may be defined for positions along the left and right ofthe array. A conductive object 1420 may be detected by the array 1400and capacitance measurement and processing circuitry (e.g., 301 or 302of FIGS. 3A and 3B) as it moves toward the right edge of the array 1400and into edge zone 1433. Conductive object 1420 may move along a path1425.

FIG. 14B illustrates a close up view of section 1440 from FIG. 14A. Path1425 is illustrated as the actual position of conductive object 1420above array 1400 from FIG. 14A. As conductive object 1420 moves intoedge zone 1433, an uncorrected position of the path may begin to differsignificantly from the actual position along path 1425. Consequently,once the position of the conductive object is calculated to be withinedge zone 1433, a correction scheme as discussed herein may be appliedto generate a corrected path 1429. In various embodiments corrected pathmay have more or less fidelity to path 1425, however, the differencebetween corrected path 1429 and path 1425 is smaller than the differencebetween path 1427 and path 1425. In still other embodiments,determination of an object to be within an edge zone may be by acalculated position, by particular unit cells recognized as peaks, orsums groups of sensors at or near the edge of the array of unit cells.

In one embodiment, the same correction scheme may be applied toconductive objects detected in each zone. In another embodiment, adifferent scheme may be applied to each axis or near of far sensors(from the connection of the electrodes to the sensing circuitry). Inthis embodiment a correction position for conductive objects near to theconnection of the electrodes of the sensing circuitry may be given by:

$\begin{matrix}{P^{\prime} = \left\{ {\begin{matrix}{{{\alpha*P} - {\left( {\alpha - 1} \right)B}},{P > {\frac{\alpha - 1}{\alpha}B}}} \\{0,{else}}\end{matrix},} \right.} & (4)\end{matrix}$where P is the uncorrected value of the X position or Y position, P′ isthe corrected value of the X position or Y position, B is the positionof the border of the edge zone, and α is a correction coefficient(greater than 1). A correction position for conductive objects far fromthe connection of the electrodes of the sensing circuitry may be givenby:

$\begin{matrix}{P^{\prime} = \left\{ {\begin{matrix}{{{\alpha*P} - {\left( {\alpha - 1} \right)B}},{P > {\frac{P_{\max} + \alpha - 1}{\alpha}B}}} \\{P_{\max},{else}}\end{matrix},} \right.} & (5)\end{matrix}$where P is the uncorrected value of the X position or Y position, P′ isthe corrected value of the X position or Y position, B is the positionof the border of the edge zone, P_(max) is the maximum possible positionvalue, and a is a correction coefficient (greater than 1).

In another embodiment, a position may be scaled for the entire activearea of the array, rather than just the zones at the edge of each axis.In this embodiment, position may be given by:

$\begin{matrix}{P^{\prime} = {\left( {P - B} \right)*\frac{Max}{P_{\max} - {2*B}}}} & (8)\end{matrix}$where P is the uncorrected value of the X position or Y position, P′ isthe corrected value of the X position or Y position, B is the positionof the border of the edge zone, and P_(max) is the maximum possibleposition value.

In another embodiment, position changed with a second order or higherorder correction. In this embodiment, position may be given by:P′=α ₂*(B−P)²+α₁*(B−P)+α₀  (9)where P is the uncorrected value of the X position or Y position, P′ isthe corrected value of the X position or Y position, B is the positionof the border of the edge zone, and α_(i) are correction coefficients(greater than 1).

For higher order corrections, position may be given by:P′=Σ _(i=0) ^(N)α_(i)(B−P)^(i)  (10)where P is the uncorrected value of the X position or Y position, P′ isthe corrected value of the X position or Y position, B is the positionof the border of the edge zone, and α_(i) are correction coefficients(greater than 1).

FIG. 15 illustrates one embodiment of a method 1500 for correctingposition of a conductive object hovering above an edge zone asillustrated in FIGS. 13, 14A, and 14B. The location of the conductiveobject may be first calculated in step 1510. If the location is withinan edge zone along the near end of the X axis in step 1515, a nearcorrection scheme may be applied in step 1520. After the near correctionscheme is applied, method 1500 may progress to decision step 1535,wherein the position is compared to an edge zone along the near end ofthe Y axis. If the position is within the edge zone along the near endof the Y axis, a near correction scheme may be applied in step 1540. If,in step 1515, the location is not within an edge zone along the near endof the X axis, method 1500 may proceed to step 1525, wherein theposition is compared to an edge zone along the far end of the X axis. Ifthe position is within the edge zone along the far end of the X axis, afar correction scheme may be applied in step 1530 before method 1500proceeds to step 1535. Similarly, if in step 1535, the location is notwithin an edge zone along the near end of the Y axis, method 1500 mayproceed to step 1545, wherein the position is compared to an edge zonealong the far end of the Y axis. If the position is within the edge zonealong the far end of the Y axis, a far correction scheme may be appliedin step 1550 and method 1500 may proceed to step 1560 and report theposition. If the position is not within any edge zone, the calculatedposition from step 1510 may be reported without any correction fromsteps 1520, 1530, 1540, or 1550.

In one embodiment, formulae similar to that of equations (5) and (6) maybe used. However, one of ordinary skill in the art would understand thatdifferent correction schemes may be used to produce positions ofhovering conductive objects that are more faithful to the actualposition of the hovering conductive objects over the array ofelectrodes. Similarly, while equations (5) and (6) are described asapplicable to near X and Y positions and far X and Y positions,respectively, one of ordinary skill in the art would understand thatdifferent correction schemes may be used for each edge zone. Similarly,one of ordinary skill would understand that, while a single coefficient,α, is applied to each equation and each zone, different coefficients maybe used with the same equations for each edge zone. Different zone sizesmay be used for different axes or for different sides of the array. Inother embodiments, the edge zones may use a calculated position or thelocation of a peak unit cell. In still other embodiments, the shape andsize of the edge zone may be changed based on the height of a measuredpeak or on the activation level (measured capacitance) on at least onecapacitance sensing electrode or combination of capacitance sensingelectrodes.

Identification and tracking of objects on a capacitance sensing array ishighly sensitive to noise. For hover detection, noise represents asignificant barrier to accurate and precise detection. The signal from ahovering conductive object may be considerably less than that of anobject in direct contact with the sensing surface. As a result, a hovermay be erroneously detected as the signal is amplified, or erroneouslydropped because of changes in measured capacitance that are the resultof system noise and not the actual change in capacitance.

FIG. 16 illustrates one embodiment of a method 1600 for detecting andconfirming a conductive object hovering above an array of electrodes asillustrated in FIGS. 10A, 10C, and 14A and detected by system 501 ofFIG. 5. Capacitance is first measured in step 1601. Capacitancemeasurement may be with both self capacitance measurement circuitry andmutual capacitance measurement circuitry. Following hover detection andposition calculation with mutual capacitance, values of mutualcapacitance at each of intersection (or unit cell) of an array may berecorded to a memory in step 1610. Mutual capacitance may be measuredwith the circuit shown in FIG. 3B and stored in a memory as shown inFIG. 5. After all of the mutual capacitance data are recorded, a commonmode filter may be applied in step 1620. The details of the common modefilter processing of step 1620 are illustrated in more detail in theembodiments shown in FIGS. 17A and 17B. The processed mutual capacitancedata, after the common mode filter of step 1620 is applied, may berecorded in step 1630 and a position of the conductive object hoveringabove the array of electrodes may be calculated in step 1640.

In parallel to the mutual capacitance measurement and processing of step1610, 1620, 1630, and 1640, a valid hover may be confirmed using selfcapacitance measurement and processing. Self capacitance may be measuredin step 1601. In one embodiment, a self capacitance measurement circuitsimilar to that shown in FIG. 3A may be used. The measured selfcapacitance values may be recorded in step 1615 and may be processed inunit cell group processing of step 1625. The processed self capacitancedata may be recorded in 1635 and a baseline value which may be used indetermination of valid hover updated in step 1645. The updated selfcapacitance baseline may be used to validate a hover detection in step1655. If the hover detection of step 1655 is validated, the hoverposition calculated in step 1640 may be reported to a host in step 1661.

In one embodiment, method 1600 may be completed by CPU 512 of FIG. 5. Invarious other embodiments, portions of method 1600 may be completed by acombination of CPU 512, tuning logic 513, and host 520 of FIG. 5.

FIG. 17A illustrates one embodiment of a common mode filter of step 1620method 1600. Mutual capacitance may be first measured in step 1701,similar to the capacitance measurement of step 1601 of method 1600 andusing a circuit similar to that shown in FIG. 3B. After the mutualcapacitance data is recorded in step 1610, method 1700 may confirm thatthe device is in hover mode and that at least one conductive object isdetected by electrodes associated with or corresponding to unit cells asillustrated in FIGS. 10A-D, 13 and 14A and capacitance measurementcircuitry and processing logic in step 1715. If there is no conductiveobject detected in step 1715 or the device is not in hover mode, method1700 may return to step 1701 and measure mutual capacitance again. Ifhover mode is active and there is at least one conductive objectdetected, each mutual capacitance sensor (unit cell or electrodeintersection) may be compared to an exclusion region in step 1725. Inone embodiment, the exclusion region may be defined by a level ofcapacitance change on each unit cell. If the mutual capacitance ischange large enough, it may be determined to be within the exclusionregion and the value of that unit cell not included, in one embodiment.In another embodiment, unit cells close enough to a peak unit cell maybe determined to be within the exclusion region, meaning that thedetermination is spatial rather than based on signals. If a unit cell isdetermined to be within the exclusion region, its values may be withheld(excluded) from a common mode filter average in step 1730. If the unitcell is not within the exclusion region, a difference value may becalculated from the measured mutual capacitance value and a common modefilter baseline value in step 1740. If the difference value is greaterthan a threshold in step 1745, the raw capacitance measurement value maybe added to a sum in step 1750. Step 1755 may ensure that all receivechannels (e.g. channel 320 of FIG. 3B) have been analyzed and theirvalues added to the sum if the unit cell is outside the exclusion region(step 1725) and the difference value greater than the threshold (step1745). If all receive channels have been processed in step 1755, anaverage of the processed receive channels may be calculated in step1760. In one embodiment, the average of the processed receive channelsmay be calculated from the summed difference values of step 1750 dividedby the total number of difference values added to the sum. Note, the sumdoes not include values from unit cells within the exclusion zone (step1725) or with difference values below the threshold (step 1745). Afterthe average is calculated in step 1760, it may be subtracted from theraw capacitance values of all of the sensors in step 1780, regardless ofwhether they are outside the exclusion zone or if their difference valueis greater than the threshold. The processed values from step 1780 maythen be recorded in step 1630 of method 1600 and the remainder to method1600 completed. In one embodiment, method 1700 may be completed by CPU512 of FIG. 5. In various other embodiments, portions of method 1700 maybe completed by a combination of CPU 512, tuning logic 513, and host 520of FIG. 5.

FIG. 17B illustrates the result 1790 of the common mode filter on themutual capacitance hover data. Line 1791 illustrates the recorded mutualcapacitance data of step 1610 of methods 1600 and 1700. Line 1795illustrates mutual capacitance data of step 1610 where all data formutual capacitance at each unit cell is treated with the samesubtraction. While the values of mutual capacitances of unit cells nearthe edge of the hover detection are zeroed out, there is a great amountof signal lost. Line 1793 illustrates mutual capacitance data of step1780 with the common mode filter process complete. Noise at the edges ofthe hover detection is zeroed out, but a greater amount of signal isretained for calculation of hover position.

FIG. 18A illustrates one embodiment of a method 1800 of the unit cellgroup processing of processing of step 1625 of method 1600. Selfcapacitance may be first measured in step 1801, similar to thecapacitance measurement of step 1601 of method 1600 and with a circuitsimilar to that of FIG. 3A. After the self capacitance data is recordedin step 1615, method 1800 may populate a plurality of virtual unit cellswith values derived from the measured self capacitance values of realunit cells. Virtual unit cells may correspond to locations on the arrayjust outside the physical area covered by the electrodes andcorresponding to unit cells as shown in FIG. 2A-B and FIGS. 10A-D.Virtual unit cells may not be part of the array of unit cells, butrather created in firmware to represent unit cells beyond the physicallimits of the array of unit cells. In one embodiment, virtual unit cellsmay be populated according to Table 1.

TABLE 1 S⁻² = S₁ − S₀ S⁻¹ = 2(S₁ − S₀) S₀ S₁ S₂ S₃One of ordinary skill in the art would understand that Table 1 isrepresentative on one side of an array of self capacitance sensors andthat a similar table may be used for the other side of the array of selfcapacitance sensors. An example is shown in Table 2.

TABLE 2 S_(N−3) S_(N−2) S_(N−1) S_(N) S_(N+1) = 2(S_(N−1) − S_(N)) S⁻² =S_(N−1) − S_(N)While Tables 1 and 2 show the same equations used for both the right andleft of the array, one of ordinary skill in the art would understandthat other calculations may be used to derive values for virtual unitcells. Additionally, while only two basic equations are shown andapplied to specific unit cells, various other equations may be used andmay differ based on the position of the virtual unit cell relative tothe rest of the array of unit cells, the axis of the virtual unit cellor the axis under test, measured capacitance values for the various unitcells, including a peak unit cell, or the mode of operation of a deviceor touchscreen controller. Virtual unit cell and real unit cell data maybe summed in step 1820 to create a new value for each real unit cell inthe self capacitance array. In one embodiment, five unit cells in a 1×5matrix, centered on each unit cell, may be summed together. In variousembodiments, different combinations of unit cells (more or less thanfive) may be used. Changing the number of unit cells may require adifferent number of virtual unit cells. In still other embodiments,additional processing may be applied to the unit cell information,including but not limited to multiplying or dividing values by variouscoefficients. The sum index from step 1820 may be compared to a hoverthreshold in step 1825 and if the sum index is greater than the hoverthreshold, a hover detected and the position from step 1640 of method1600 reported to the host in step 1661. If the sum index is not greaterthan the hover threshold, the hover position calculated in step 1640 maynot be reported to the host in step 1661. In one embodiment, method 1800may be completed by CPU 512 of FIG. 5. In various other embodiments,portions of method 1800 may be completed by a combination of CPU 512,tuning logic 513, and host 520 of FIG. 5.

FIG. 18B illustrates the result 1890 of the sum index and hoverthreshold comparison of method 1800. The values of lines 1895 (rawcapacitance data from step 1615) and 1893 (processed capacitance datafrom step 1614 and 1820) are compared to the hover threshold 1891. Ifthe raw values are less than the threshold and the processed values aregreater than the threshold, a valid hover is detected in step 1655.

Once a valid hover is detected, the next step may be to determine theposition of that hover on the array.

FIG. 19A illustrates an array 1901 of mutual capacitance unit cells withcapacitance changes similar to those shown in FIG. 10C. Peak unit cell1910 is identified using the 5×5 matrix of unit cells as illustrated inFIG. 10C and described in FIG. 11A. FIG. 19A illustrates the calculationof an EdgeCutoff that may be used to determine which unit cells are usedto calculate the position of a hover over the array 1901 of mutualcapacitance unit cells. Because of noise at the edges of a hover, theremay exist jitter on the position calculation of a hover that createsimprecision in the position reported to the host and viewed by the user.Determining which unit cells are used in calculating the position bysetting a threshold that is derived, in part, from the measuredcapacitance changes may improve performance and the user experience.After peak unit cell 1910 is identified, the center three 1×5 matricesof cells about the peak may be summed. In the example in FIG. 19, therow with peak unit cell 1910 is summed to equal 84 (14+21+23+16+10) andthe rows immediately above and below peak unit cell 1910 are summed toequal 97 and 94, respectively. The column with peak unit cell 1910 issummed to equal 106 (15+24+23+23+21) and the columns immediate to theleft and right of peak unit cell 1910 are summed to equal 94 and 82,respectively. The three rows and three columns about peak unit cell 1910may then be summed to yield a row sum of 275 and a column sum of 282.These sums may be multiplied by a scalar to yield an EdgeCutoff value.In the example in FIG. 19, the scalar is 10/54, which yields anEdgeCutoff for rows of 51 and an EdgeCutoff for columns of 52. Usingthese EdgeCutoffs, rows and columns are included or not included basedon their 1×5 matrix sum about peak unit cell 1910. While a 1×5 matrix isshown in FIG. 19, one of ordinary skill in the art would understand thatin various embodiments, different shapes and sizes of matrices may beused. For example 1×3, 1×4, or even 1×87 matrices may be used. The sizeof the matrix may be set during development in one embodiment. Inanother embodiment, the size of the matrix may be set based on the unitcell or column or row under test, the signal level of a peak unit cell,or a mode of operation of the device or touchscreen controller.

In the example of FIG. 19A, there are six columns with values above theEdgeCutoff and six rows with values above the EdgeCutoff. These six rowsand six columns may be used in calculating the position of the hover.The scalar of 10/54 may be determined in development and design of thetouchscreen in one embodiment. In another embodiment, there may bemultiple values stored in the device, either in the touchscreencontroller or in the host, that may be used based on varied capacitancechange values or user settings. In one embodiment, a user may be able toincrease or decrease the scalar by entering a settings window andadjusting the sensitivity of the hover detection and the accuracy of theposition, relative to other touch parameters. For example, decreasingthe EdgeCutoff may provide greater range in calculation of hoverposition, but may also introduce more jitter into the positioncalculation. If a user values sensitivity over precision, they may choseto decrease the value of the scalar.

FIG. 19B illustrates an embodiment of the EdgeCutoff and how it may beapplied to the summed values in determining which rows are used incalculation of the position of the hover and how much of each column androw are used. While FIG. 19A illustrates only the calculation ofposition along rows, one of ordinary skill in the art would understandthat that a similar method and calculation may be used for columns. Eachrow with values above the EdgeCutoff 1930 is shown as a histogram withthe value at the top. Rows 2 and 9 are below EdgeCutoff 1930 and aretherefore not used in the calculation of the hover position. Rows 3 and8 are above EdgeCutoff 1930, but they are the first rows on each side ofpeak unit cell 1910 that are included and their contributions maytherefore be discounted. Because row 3 is barely above EdgeCutoff 1930and row 2 is so far below EdgeCutoff 1930, only one third (18 of 54) ofthe value of row 3 may be included in the position calculation. Becauserow 8 may be higher above EdgeCutoff 1930 and because row 9 is closer toEdgeCutoff 1930, more of row 8 is included in the position calculation(86%; 59 of 69).

Because a hovering object may exert less influence over measuredcapacitance levels of an array of capacitance sensing electrodes, hoverdetection may be susceptible to false detections or rapidly changingpositions due to proximity of other objects near or on the array ofcapacitance sensing electrodes. In various embodiments, to maintain aposition, some level of hysteresis may be used.

FIG. 20 illustrates a method 2000 for maintaining position of hover inthe presence of other signals (such as another hover or a grip) or highnoise. Method 2000 may be used to ensure that a hover detection is madeand tracked over the screen as a user's hand gets closer to the array ofelectrodes or if a user's fingers holding the device begin to change thecapacitance of electrodes along the edge of the array of electrodes.Mutual capacitances for each unit cell may be measured in step 2010 andthe sum of each unit cell and the 24 unit cells in a 5×5 matrix aboutthat unit cell is calculated in step 2010. This may be similar to thatdescribed with regard to FIG. 10C. After each unit cell has a calculatedsum, a peak sensor (or sensors) is identified in step 2030, for exampleas shown and described in FIGS. 10 11, and 12. Using a previouslyidentified peak unit cell, the presently identified peak unit cell maybe compared to see if it is close to or far from the previous peak. Ifthe presently identified peak unit cell is close to the previous peakunit cell, a normal hover threshold may be applied in step 2042. Invarious embodiments, this may mean that normal scalars are used (seeEdgeCutoff from FIGS. 19A and 19B) or it may mean that values ofcapacitance changes necessary to detect that a hover is even present aremaintained. If the presently identified peak unit cell is far from theprevious peak a hysteresis may be applied to the various hoverthresholds in step 2044. In various embodiments, scalars may beincreased for the EdgeCutoff, or the values of capacitances necessary todetect that a hover is present may be raised. With the hover thresholdsset in steps 2042 and 2044, the capacitance values may be analyzed todetect a hover in step 2045. If the hover requirements are not met instep 2045, method 2000 may return to step 2010 and measure the mutualcapacitances again. If the hover requirements are met in step 2045, theheight (Z position) of the object above the array and the object sizemay be calculated in step 2050. For close peaks identified in step 2035,the object size from step 2050 may be compared to a threshold for closeobjects in step 2053. If the object size from 2050 is greater than thethreshold for close objects in step 2053, the position of the object maybe calculated in step 2060 and recorded in step 2070. If the object sizefrom 2050 is not greater than the threshold for close objects in step2053, method 2000 may return a state of “no hover” in step 2080 and mayreturn to step 2010 and measure mutual capacitances again. For far peaksidentified in step 2035, the object size from step 2050 may be comparedto a threshold for far objects in step 2057. If the object size from2050 is greater than the threshold for far objects in step 2057, theposition of the object may be calculated in step 2060 and recorded instep 2070. If the object size from 2050 is not greater than thethreshold for far objects in step 2057, method 2000 may return a stateof “no hover” in step 2080 and may return to step 2010 and measuremutual capacitances again.

Method 2000 of FIG. 20 may be used to ignore extraneous or unintendedinteraction with the array that may register as a hover by usingexpected values to increase or decrease the criteria for detecting ahover. For a hover detection that is close to the expected position, thethresholds for qualifying a hover may be relaxed compared to thequalifications if a hover detection that is farther from the expectedposition. This means that a hover that is moving rapidly high above thearray is more likely to be dropped than a finger at the same height thatmoves more slowly.

FIG. 21 illustrates addition steps in method 2100 for determining whichpeak unit cell to use in detecting or maintaining a hover, as well ascalculating the hover position. Method 2100 may begin by recordingpositions for close and far objects in step 2110, similar to step 2070of FIG. 20. If a large object was previously detected in step 2115,method 2100 may then determine if a large object is presently detectedin step 2125. If a large object is presently detected in step 2125, alarge object debounce counter may be decremented in step 2130 and ahover not reported in step 2190. If a large object was not previouslydetected in step 2115 or a large object is not detected in step 2125, apeak unit cell may be detected in step 2135. If a peak unit cell is notdetected, a hover is not reported in step 2190. If a peak unit cell isdetected in step 2135, and the far peak unit cell is much higher thanthe close peak, the far peak is used for hover position calculation instep 2154. If the far peak unit cell is not much higher than the closepeak unit cell, the close peak unit cell is used for hover positioncalculation in step 2152. Hover position may be updated based on theidentified peak unit cells from steps 2152 and 2154 in step 2160. If thepeak unit cell is not part of a large object in step 2165, the finalposition is calculated and a hover contact is report to the host in step2180. If the peak unit cell is part of a large touch, a large objectdebounce counter may be initialized in step 2170 and a hover notreported in step 2190.

Once a hover has been detected and verified the position of that hovermay be calculated using standard centroid calculation methods, such asEquation (3). However, the low signal level of a hover may causesignificant jitter in the detected position and reduce the usability ofa touchscreen device with hover capability enabled. As a result,different position calculation algorithms may be used to for hoveringcontact types than for objects and contact types with greater capacitiveinfluence on the measured capacitance data of the various capacitancesensing electrodes and measurement circuitry.

FIG. 22A illustrates an embodiment of a method 2201 for calculating theposition of a hover contact on an array of electrodes using a medianunit cell and the pitch of the electrodes of the array. All unit cellsused in calculation of position may be summed in step 2210. In oneembodiment, the unit cells used for hover position calculation aredetermined using the method outlined with regard to FIGS. 19A and 19B.In another embodiment, a straight usage of a matrix of unit cells arounda peak as shown in FIGS. 10B-C and 11 may be used. In various otherembodiments, all unit cells in the array or other subsets of unit cellsmay be use. After all of the signals from all relevant unit cells aresummed in step 2210, the sum my then be divided by 2 in step 2220.Starting with the first unit cell in the array to be used in positioncalculation, values on each unit cell are added together in step 2230.The value of a first unit cell, S_(N), may be added to the value of asecond unit cell, S_(N+1). The value of S_(N) and S_(N+1) may then berecorded as a total, S_(TOTAL) in step 2240. The value of S_(TOTAL) maythen be compared to the sum of all unit cells divided by 2 from step2220 in step 2245. If S_(TOTAL) is less than half of the sum of all unitcells, the signal from the next unit cell may be added to S_(TOTAL) instep 2250 and the comparison of step 2245 may be repeated. If S_(TOTAL)is greater than half of the sum of all unit cells, a ratio, R, may becalculated by subtracting half of the sum of all unit cells fromS_(TOTAL) and dividing that value by the value of the unit cell,S_(HALF), that cause S_(TOTAL) to pass the value of half of the sum ofall unit cells in step 2260. Position may then be calculated as theratio, R, times the unit cell pitch plus the number of previous unitcells times the unit cell pitch in step 2270. Dividing the sum of allrelevant unit cells by two is not intended to be limiting. In someembodiments, different values may be used in the denominator, includingwhole numbers or fractions. In still other embodiments, the sum of allrelevant unit cells may be divided into more than two groups to providedifferent ranges or possibilities of identified unit cells

FIG. 22B illustrates an example of method 2201 of FIG. 22A. The positionusing a standard centroid calculation is shown as centroid position2280. However, this position may be unnecessarily effected by the sensorvalues at the right edge of the contact. By using method 2201 of FIG.22A, the median position 2282 is shown to be slightly left of thecentroid position 2280. In the example shown in FIG. 22B, S_(TOTAL) is270, which means that the position is calculated as 28.125% acrosssensor 3. If standard centroid calculation is used, the position iscalculated as 44.34%, according to equation (3).

FIGS. 23A, 23B, and 23C illustrate various embodiments of ratios ofvalues on unit cells for different contact types near the edge of anarray of capacitance sensing electrodes. These ratios may be used todifferentiate between the different contacts and apply differentposition calculation and other processing algorithms to the capacitanceinformation. The sensors used in calculation may be determined similarlyto those shown in FIGS. 19A and 19B.

FIG. 23A illustrates a grip contact on the edge of an array. A peak unitcell may be identified and a pair of 1×5 matrices about that peak unitcell summed. The ratio of the outer most matrix to the more centeredmatrix may then be calculated and recorded. For the grip contact of FIG.23A, the sum of the 1×5 matrix at the edge of the array is 236 and thesum of the more centered 1×5 matrix is 64, yielding a ratio of 3.7.

FIG. 23B illustrates a hover contact over the edge of an array. A peakunit cell may be identified and a pair of 1×5 matrices about that peakunit cell summed as described in with regard to FIG. 23A. The ratio ofthe outer most matrix to the more centered matrix may then be calculatedand recorded. For the hover contact over the edge of an array of FIG.23B, the sum of the 1×5 matrix at the edge of the array is 68 and thesum of the more centered 1×5 matrix is 45, yielding a ratio of 1.5

FIG. 23C illustrates a hover contact near the edge of an array, but notover it. A peak unit cell may be identified and a pair of 1×5 matricesabout that peak unit cell summed as described in with regard to FIGS.23A and 23B. The ratio of the outer most matrix to the more centeredmatrix may then be calculated and recorded. For the hover contact nearthe edge of an array of FIG. 23C, the sum of the 1×5 matrix at the edgeof the array is 124 and the sum of the more centered 1×5 matrix is 111,yielding a ratio of 1.1.

The matrices of FIGS. 23A, 23B, and 23C, while illustrated as 1×5matrices, may have different dimensions and shapes. In anotherembodiment, the matrices may be determined during the manufacturingprocess for each touchscreen unit and burned into the controller atproduction. In still another embodiment, the matrices may be changed orturned by the user through a settings menu and interface. In someembodiments a user may not change the dimensions and shapes of thematrices directly. Rather settings on sensitivity or response may changea variety of parameters, of which the matrix shape may be one.

The various ratios of FIGS. 23A, 23B, and 23C may be compared toexpected values and if they are in certain ranges, the contactscorrectly identified and processed accordingly. In one embodiment, theranges may be determined during development and burned into thecontroller during production. In another embodiment, the ranges may bedetermined during the manufacturing process for each touchscreen unitand burned into the controller at production. In still anotherembodiment, the ratios may be changed or otherwise altered by the userthrough a settings menu and interface. In some embodiments a user maynot change the ratio thresholds directly. Rather settings on sensitivityor response may change a variety of parameters, of which the ratiothresholds may be one.

Furthermore, while FIGS. 23A, 23B, and 23C show detection of objects onvertical edges of an array of unit cells, one of ordinary skill in theart would understand that the same or similar scheme may be used alonghorizontal edges of an array of unit cells.

FIG. 24 illustrates one embodiment of a method 2400 for determining whattype of contact is present according the embodiments in FIGS. 23A, 23B,and 23C. Mutual capacitance may be first measured in step 2410. In oneembodiment, mutual capacitance may be measured according to the circuitillustrated in FIG. 3B. In one embodiment, the measured mutualcapacitance may be represented as the difference between a measuredvalue and a baseline value that is maintained for each unit cell orglobally for the array. A peak unit cell may then be identified in step2420. The peak unit cell of step 2420 may be identified in a mannersimilar to that shown in FIGS. 10B and 10C, as well as FIGS. 11A and11B. After the peak unit cell is identified in step 2420, active unitcells may be identified in step 2430 in a manner similar to that shownin FIG. 19A. The contact ratio of the active unit cells as illustratedin FIG. 23 may be calculate in step 2440. In one embodiment, the contactratio of step 2440 may be calculated as the sum of a first 1×5 matrixabout a peak unit cell at the edge of the array divided by a second 1×5matrix about a peak unit cell one column or row more central than thefirst 1×5 matrix. While the embodiment shown in FIG. 23 illustrates onlya pair of 1×5 matrices, one of ordinary skill in the art wouldunderstand that matrixes of greater length and width may be used.Additionally, while the embodiments of FIGS. 23 and 24 divide the outermost matrix by the adjacent matrix, one of ordinary skill in the artwould understand that this may be reversed than that the inverse of theratios uses in the same manner. Once the contact ratio is calculated instep 2440, it may be compared to a number of ranges in step 2445. If theratio of step 2440 is within a “grip” range, a grip contact may beidentified in step 2452 and processed with grip heuristics in step 2462.If the ratio of step 2440 is within a “hover on” range, a hover on theedge of the array may be identified in step 2454 and processed with theappropriate hover heuristics in step 2465. If the ratio of step 2440 iswithin a “near hover” range, a hover near the edge of the array may beidentified in step 2456 and processed with the appropriate hoverheuristics in step 2465.

FIG. 25A illustrates the maximum signals detected for various touchtypes, including hover, hover near an edge, a thin glove, a 2 mm stylus,no touch, a thick glove and a 1 mm stylus. These maximum signals may beused to define partitions or ranges with the regions of FIG. 26. Ifthere is touch or hover detected, the received signals may represented anoise floor, from which difference values may be calculated andprocessed to detect the various object and contact types.

FIG. 25B illustrates the relationship between the value of a peak unitcell and the surrounding unit cells for the various object and contacttypes. A typical finger has a high peak unit cell value and falls offfrom there at a rate that is below a stylus, but above a gloved fingeror hover. A gloved finger and a stylus have similar peak unit cellsvalues, but the lower contact area of a stylus results in a much steeperdrop off of signal from unit cells surrounding the peak unit cell. Ahover and a stylus may have different peak unit cell values, butintegrating the value of the peak unit cell and the surrounding unitcell, may result in similar values.

FIG. 26 illustrates a chart with various 5×5 sums of sensors similar asthose illustrated in FIGS. 10B and 10D on the Y-axis and the peak sensorvalue on the X-axis to show that various touch types have peak valuesand sums that correspond to specific regions and may be categorized whena touch controller is in various touch modes.

FIGS. 27A, 27B, and 27C illustrate various partitions or ranges fordetecting a contact type when operating in various modes. The 5×5 matrixsum about a peak unit cell is calculated similar as those illustrated inFIGS. 10B and 10D and plotted on the Y axis. The peak unit cell value isplotted on the X axis. Where the point lies within the variouspartitions is used to identify the contact type. For FIGS. 27A, 27B, and27C, there are four possible partitions: idle/hover 2711, gloved finger2712, stylus 2713, and bare finger 2714. If partition 2711 is active,the various methods for identifying and calculating the position of ahover of the preceeding figures may be used.

FIG. 27A illustrates a plot 2701 of partitions or ranges for atouchscreen device operating in finger mode. In one embodiment, all peakunit cells with values less than a value of a first touch threshold 2721are identified as “idle” or corresponding to no contact in directcontact the array. In one embodiment, peak unit cells and the values ofeach may be determined and calculated according to FIGS. 10, 11, and 12.For peak unit cell values greater than the first touch threshold 2721and less than a maximum glove peak 2723, which is representative of thehighest peak value for which a gloved finer may be detected, with 5×5sums (as illustrated in FIGS. 10B and 10D) that are greater than thepeak unit cell value multiplied by a value to create a matrix threshold2724 are identified as a gloved finger. For peak values greater than thefirst touch threshold 2721 with 5×5 sums that are less than the peakunit cell value multiplied by a value to create a matrix threshold 2726and greater than the peak 2125 are identified as a stylus. All otherpoints are identified as a bare finger directly on the array.

FIG. 27B illustrates a plot 2702 of partitions or ranges for atouchscreen device operating in glove mode. In one embodiment, all peakunit values less than a value of a minimum value that can be used toidentify a gloved finger 2731 are identified as “idle” or correspondingto no contact in direct contact the array. In one embodiment, peak unitcells and the values of each may be determined and calculated accordingto FIGS. 10, 11, and 12. For peak values greater than the minimum valuethat can be used to identify a gloved finger 2731 and less than themaximum signal that can be used to identify a gloved finger 2733 with5×5 sums (as illustrated in FIGS. 10B and 10D) that are not with apartition bounded by the value of the peak along the Y axis (line 2726),the maximum value of a 5×5 matrix that can be detected as a stylus 2726and peak unit cell values bounded by matrix threshold 2724 and stylusthreshold 2732, a gloved finger is identified. For peak values greaterthan the stylus threshold 2732 with 5×5 sums less than the maximum valueof a 5×5 matrix that can be detected as a stylus 2726 and greater thanpeak on the Y axis 2125 are identified as a stylus. All other points areidentified as an uncovered finger directly on the array. For pointswithin a partition bounded by the peak on the Y axis 2726, the maximumvalue of a 5×5 matrix that can be detected as a stylus 2726 and peakvalues bounded by matrix threshold 2724 and stylus threshold 2732, astylus is identified. All other points are identified as a bare fingerdirectly on the array.

FIG. 27C illustrates a plot 2703 of partitions or ranges for atouchscreen device operating in stylus mode or hover mode. In oneembodiment, all peak values less than a value of stylus threshold 2732are identified as “idle” or corresponding to no contact in directcontact the array. In one embodiment, peak unit cells and the values ofeach may be determined and calculated according to FIGS. 10, 11, and 12.For peak values greater than stylus threshold 2732 and less than maximumglove peak 2723 with 5×5 sums (as illustrated in FIGS. 10B and 10D) thatare greater than an increased peak value 2745 are identified as a glovedfinger. For peak values greater than stylus threshold 2732 with 5×5 sumsless than peak value 2745 or peak values greater than maximum glove peak2723 and less than a boundary between stylus and bare fingers 2744greater are identified as a stylus. All other points are identified as abare finger directly on the array.

FIG. 28 illustrates a method 2800 for determining the correct mode of atouchscreen based on the maximum signal (value of a peak unit cell) anda number of thresholds, according to one embodiment. Capacitance of eachintersection may be measured in step 2802 and maximum difference valuescalculated in step 2804. If hover mode is active in step 2805, athreshold is set by the hover mode settings in step 2810 and the maximumdifference value from step 2804 is compared to that threshold in step2813. If the maximum difference value is less than the threshold, nocontact is detected and the touchscreen enters an idle mode in step2818. If the maximum difference value exceeds the threshold, hover modeis maintained in step 2820. If hover mode is not active in step 2805,the threshold is set by whatever the previous mode was in step 2808. Themaximum difference value is compared to the threshold from the previousmode in step 2815 and, if it is less than the threshold, no contact isdetected and the touchscreen enters an idle mode in step 2818. If it isgreater than the threshold from the previous mode, the devicetransitions from hover mode to whatever the previous mode was in step2822. If stylus mode is active in step 2825, the maximum differencevalue from step 2804 is compared to a threshold for a transition fromstylus detection to finger detection in step 2827 and if the maximumdifference values are greater than that threshold, the touchscreendevice enters finger mode in step 2830. If glove mode is active in step2833, the maximum difference value from step 2804 is compared to athreshold for a transition from glove detection to finger detection instep 2835 and if the maximum difference values are greater than thatthreshold, the touchscreen device enters finger mode in step 2838. If itdoes not, the previous mode is entered and the appropriate thresholdsfor that mode are used.

FIG. 29 illustrates another embodiment of a method 2900 for detectingobject types and contact types from different modes, according to oneembodiment. The maximum different values may be first calculated in step2902, similar to step 2804 of method 2800. A mode may be determined instep 2905, between stylus mode, finger mode, or glove mode. If thedevice is in Stylus mode in step 2906, the peak unit cell and the 5×5matrix of unit cells about the peak unit cell (as illustrated in FIGS.10B and 10D) may be plotted on according to FIG. 27C. If the peak unitcell and the 5×5 matrix of unit cells falls within the glove partitionof FIG. 27C in step 1915, method 2900 may determine if the mode changeis within a debounce time in step 2917. If the mode change is within thedebounce time, the mode switch may be set to “pending” in step 1918 andStylus mode may be maintained in step 2924. Likewise, if the peak unitcell and the 5×5 matrix of unit cells does not fall within the glovepartition of FIG. 27C in step 1915, Stylus mode may be maintained instep 2924. However, the peak unit cell and the 5×5 matrix of unit cellsfalls within the glove partition of FIG. 27C in step 1915, and theswitch is outside a debounce time in step 2917, method 2900 may changethe device mode to Glove mode in step 2922 and return that mode in step2924.

If the device is in glove mode in step 2910, the peak unit cell and the5×5 matrix of unit cells about the peak unit cell (as illustrated inFIGS. 10B and 10D) may be plotted on according to FIG. 27B. If the peakunit cell and the 5×5 matrix of unit cells falls within the styluspartition of FIG. 27B in step 2925, method 2900 may determine if themode change is within a debounce time in step 2927. If the mode changeis within the debounce time the mode switch may be set to “pending” instep 2928 and glove mode may be maintained in step 2924. Likewise, ifthe peak unit cell and the 5×5 matrix of unit cells does not fall withinthe stylus partition of FIG. 27C in step 2925, glove mode may bemaintained in step 2942. However, the peak unit cell and the 5×5 matrixof unit cells falls within the glove partition of FIG. 27C in step 2925,and the switch is outside a debounce time in step 2957, method 2900 maychange the device mode to stylus mode in step 2940 and return that modein step 2942.

If the device is in finger mode in step 2908, method 2900 may firstdetermine if there is a switch to glove mode pending in step 2945. Ifthere is not, the peak unit cell and the 5×5 matrix of unit cells aboutthe peak unit cell (as illustrated in FIGS. 10B and 10D) may be plottedon according to FIG. 27A. If the peak unit cell and the 5×5 matrix ofunit cells falls within the stylus partition of FIG. 27B in step 2955,method 2900 may determine if the mode change is within a debounce timein step 2957. If the mode change is within the debounce time, the modeswitch may be set to “pending” in step 2958 and finger mode many bemaintained in step 2972. Likewise, if the peak unit cell and the 5×5matrix of unit cells does not fall within the stylus partition of FIG.27C in step 2955, finger mode may be maintained in step 2972. However,the peak unit cell and the 5×5 matrix of unit cells falls within thestylus partition of FIG. 27C in step 2955, and the switch is outside adebounce time in step 2957, method 2900 may change the device mode tostylus mode in step 2970 and return that mode in step 2972.

If there is a glove switch pending in step 2945, the peak unit cell andthe 5×5 matrix of unit cells about the peak unit cell (as illustrated inFIGS. 10B and 10D) may be plotted on according to FIG. 27A. If the peakunit cell and the 5×5 matrix of unit cells falls within the glovepartition of FIG. 27B in step 2975, method 2900 may determine if themode change is within a debounce time in step 2977. If the mode changeis within the debounce time, the mode switch may be set to “pending” instep 2958 and finger mode may be maintained in step 2992. Likewise, ifthe peak unit cell and the 5×5 matrix of unit cells does not fall withinthe glove partition of FIG. 27C in step 2975, Finger mode may bemaintained in step 2992. However, the peak unit cell and the 5×5 matrixof unit cells falls within the glove partition of FIG. 27C in step 2975,and the switch is outside a debounce time in step 2977, method 2900 maychange the device mode to glove mode in step 2990 and return that modein step 2992.

FIG. 30 illustrates one embodiment of a state diagram 3000 for enteringinto hover mode when if a large object is detected. State diagram 3000may begin in look for hover mode 3010 or look for touch mode 3012. If ahovering object is detected, state diagram 3000 may enter a valid hoverstate 3020. If a large hovering object is detected, state diagram mayenter a large hover object state 3030 from which only two options arepossible: look for hover mode 3010 or valid finger mode 3040. This meansthat a valid hover state may not be entered if a large object isdetected hovering over the array.

In the above description, numerous details are set forth. It will beapparent, however, to one of ordinary skill in the art having thebenefit of this disclosure, that embodiments of the present inventionmay be practiced without these specific details. In some instances,well-known structures and devices are shown in block diagram form,rather than in detail, in order to avoid obscuring the description.

Some portions of the detailed description are presented in terms ofalgorithms and symbolic representations of operations on data bitswithin a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here and generally,conceived to be a self-consistent sequence of steps leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared and otherwise manipulated. It has provenconvenient at times, principally for reasons of common usage, to referto these signals as bits, values, elements, symbols, characters, terms,numbers or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as “integrating,” “comparing,” “balancing,” “measuring,”“performing,” “accumulating,” “controlling,” “converting,”“accumulating,” “sampling,” “storing,” “coupling,” “varying,”“buffering,” “applying,” or the like, refer to the actions and processesof a computing system, or similar electronic computing device, thatmanipulates and transforms data represented as physical (e.g.,electronic) quantities within the computing system's registers andmemories into other data similarly represented as physical quantitieswithin the computing system memories or registers or other suchinformation storage, transmission or display devices.

The words “example” or “exemplary” are used herein to mean serving as anexample, instance or illustration. Any aspect or design described hereinas “example” or “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects or designs. Rather, use ofthe words “example” or “exemplary” is intended to present concepts in aconcrete fashion. As used in this application, the term “or” is intendedto mean an inclusive “or” rather than an exclusive “or.” That is, unlessspecified otherwise, or clear from context, “X includes A or B” isintended to mean any of the natural inclusive permutations. That is, ifX includes A; X includes B; or X includes both A and B, then “X includesA or B” is satisfied under any of the foregoing instances. In addition,the articles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Moreover, use of the term “an embodiment” or “one embodiment” or“an implementation” or “one implementation” throughout is not intendedto mean the same embodiment or implementation unless described as such.

Embodiments described herein may also relate to an apparatus forperforming the operations herein. This apparatus may be speciallyconstructed for the required purposes, or it may comprise ageneral-purpose computer selectively activated or reconfigured by acomputer program stored in the computer. Such a computer program may bestored in a non-transitory computer-readable storage medium, such as,but not limited to, any type of disk including floppy disks, opticaldisks, CD-ROMs and magnetic-optical disks, read-only memories (ROMs),random access memories (RAMs), EPROMs, EEPROMs, magnetic or opticalcards, flash memory, or any type of media suitable for storingelectronic instructions. The term “computer-readable storage medium”should be taken to include a single medium or multiple media (e.g., acentralized or distributed database and/or associated caches andservers) that store one or more sets of instructions. The term“computer-readable medium” shall also be taken to include any mediumthat is capable of storing, encoding or carrying a set of instructionsfor execution by the machine and that causes the machine to perform anyone or more of the methodologies of the present embodiments. The term“computer-readable storage medium” shall accordingly be taken toinclude, but not be limited to, solid-state memories, optical media,magnetic media, any medium that is capable of storing a set ofinstructions for execution by the machine and that causes the machine toperform any one or more of the methodologies of the present embodiments.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct a more specializedapparatus to perform the required method steps. The required structurefor a variety of these systems will appear from the description below.In addition, the present embodiments are not described with reference toany particular programming language. It will be appreciated that avariety of programming languages may be used to implement the teachingsof the embodiments as described herein.

The above description sets forth numerous specific details such asexamples of specific systems, components, methods and so forth, in orderto provide a good understanding of several embodiments of the presentinvention. It will be apparent to one skilled in the art, however, thatat least some embodiments of the present invention may be practicedwithout these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present invention. Thus, the specific details set forth above aremerely exemplary. Particular implementations may vary from theseexemplary details and still be contemplated to be within the scope ofthe present invention.

It is to be understood that the above description is intended to beillustrative and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

The invention claimed is:
 1. A method comprising: at a touch-sensitivedevice operating in a first operational mode, wherein the firstoperational mode is associated with a two-dimensional chart partitionedinto a plurality of regions, each region corresponding to a respectivecontact type: measuring capacitance on a plurality of mutual capacitancesensors, each mutual capacitance sensor corresponding to a unit cell inan array of unit cells; identifying a peak unit cell from the array ofunit cells based on the measured capacitances; calculating a sum ofmeasured capacitances for a plurality of unit cells surrounding theidentified peak unit cell, wherein the plurality of unit cells is lessthan all of the array of unit cells; locating a point in thetwo-dimensional chart whose x-coordinate is the measured capacitance ofthe peak unit cell and whose y-coordinate is the calculated sum; anddetermining a contact type that corresponds to a region, in the chart,that contains the point.
 2. The method of claim 1, wherein the contacttype is selected from the group consisting of a bare finger, a glovedfinger, a stylus, and a contact hovering above the array.
 3. The methodof claim 1, wherein the first operational mode is selected from thegroup consisting of a bare finger detection mode, a stylus detectionmode, and a gloved finger detection mode.
 4. The method of claim 1,wherein the plurality of unit cells surrounding the peak unit cell is aband of unit cells adjacent to the peak unit cell.
 5. The method ofclaim 4, wherein a width of the band of unit cells adjacent to the peakunit cell is a single unit cell wide.
 6. The method of claim 4, whereina width of the band of unit cells adjacent to the peak unit cell is twounit cells wide.
 7. The method of claim 4, wherein a width of the bandof unit cells adjacent to the peak unit cell is predetermined.
 8. Themethod of claim 1, wherein: the array of unit cells includes a firstnumber of unit cells; the plurality of unit cells includes a secondnumber of unit cells; and the second number of unit cells is less thanthe first number of unit cells.
 9. The method of claim 8, wherein thesecond number of unit cells is a predetermined number of unit cells. 10.The method of claim 1, wherein: the chart is a first chart; the firstoperational mode corresponds to a first contact type; the plurality ofpartitioned regions is a first plurality of partitioned regions; themethod further comprises, in response to determining that the determinedcontact type differs from the first contact type, transitioning from thefirst operational mode to a second operational mode that corresponds tothe determined contact type; and the second operational mode isassociated with a second chart partitioned into a second plurality ofregions, each region corresponding to a respective contact type.
 11. Themethod of claim 10, wherein a boundary of at least one region in thesecond plurality of regions differs from a boundary of a correspondingregion in the first plurality of regions.
 12. The method of claim 10,wherein: a region, in the first chart, corresponding to the firstcontact type, has a first area; a region, in the second chart,corresponding to the first contact type, has a second area; and thesecond area is smaller than the first area.
 13. The method of claim 1,further comprising in response to determining that the determinedcontact type corresponds to the first operational mode, reporting aposition of a touch event based on the measured capacitances.
 14. Atouch-sensitive device comprising: an array of unit cells; a controlleroperating in a first operational mode, wherein the first operationalmode is associated with a two-dimensional chart partitioned into aplurality of regions, each region corresponding to a respective contacttype, the controller being configured to: measure capacitance on aplurality of mutual capacitance sensors, each mutual capacitance sensorassociated with a unit cell in the array of unit cells; identify a peakunit cell from the array of unit cells based on the measuredcapacitances; calculate a sum of measured capacitances for a pluralityof unit cells surrounding the identified peak unit cell, wherein theplurality of unit cells is less than all of the array of unit cells;locate a point in the two-dimensional chart whose x-coordinate is themeasured capacitance of the peak unit cell and whose y-coordinate is thecalculated sum; and determine a contact type that corresponds to aregion, in the chart, that contains the point.
 15. The touch-sensitivedevice of claim 14, wherein the contact type is selected from the groupconsisting of a bare finger, a gloved finger, a stylus, and a contacthovering above the array.
 16. The touch-sensitive device of claim 14,wherein the first operational mode is selected from the group consistingof a bare finger detection mode, a stylus detection mode, and a glovedfinger detection mode.
 17. A touchscreen controller configured to: whileoperating in a first operational mode, wherein the first operationalmode is associated with a two-dimensional chart partitioned into aplurality of regions, each region corresponding to a respective contacttype: measure capacitance on a plurality of mutual capacitance sensors,each mutual capacitance sensor associated with a unit cell in an arrayof unit cells; identify a peak unit cell from the array of unit cellsbased on the measured capacitances; calculate a sum of measuredcapacitances for a plurality of unit cells surrounding the identifiedpeak unit cell, wherein the plurality of unit cells is less than all ofthe array of unit cells; locate a point in the two-dimensional chartwhose x-coordinate is the measured capacitance of the peak unit cell andwhose y-coordinate is the calculated sum; and determine a contact typethat corresponds to a region, in the chart, that contains the point. 18.The touchscreen controller of claim 17, wherein the contact type isselected from the group consisting of a bare finger, a gloved finger, astylus, and a contact hovering above the array.
 19. The touchscreencontroller of claim 17, wherein the first operational mode is selectedfrom the group consisting of a bare finger detection mode, a stylusdetection mode, and a gloved finger detection mode.